In a conventional branch of a bank, each teller has a workstation connected to a machine for dispensing, accepting or recycling physical tokens of monetary value (“cash”), typically in the form of bank notes and/or coins. Such a machine may be referred to as a teller cash dispenser (TCD), teller cash acceptor (TCA) or teller cash recycler (TCR), the latter being able to both dispense and accept cash and tore-dispense accepted cash to other customers. Each machine is a peripheral connected to only one or perhaps two teller workstations, each connection being a dedicated, one-to-one physical connection in the form of a cable such as a serial cable.
Each teller's workstation may also be separately connected to a core bank system via a network of the branch. The core system is where the data of the customers' bank accounts are held. To process a transaction such as dispensing cash, the teller may use a dual keyed model whereby he or she first uses the workstation to key in the transaction from the workstation to the core network, and if the core network approves the transaction it returns an approval to the teller's work station. The teller then uses the workstation to separately key in the same transaction from the workstation into the peripheral cash-handling machine in order for the workstation to control the machine to complete the transaction. This way the cash-handling machine is kept isolated from the wider network. Alternatives to the dual keyed model include screen scraping, graph integration or full integration.
Traditionally, a given cash-handling machine such as a TCR is rarely shared between more than two tellers. For example, it is important to know whose cash is being dispensed. To that end only one teller should be able to cause the machine to dispense cash at any one time. In the case of one workstation per machine this is relatively straightforward. In the case of two, if the cash-handling machine does receive a transaction request from the connection with the workstation of teller A while cash is currently being dispensed to the other teller B, the cash-handling machine will block the request and return a message to A's workstation saying the machine is busy.